[3.13.y.z extended stable] Patch "can: peak_pci: prevent use after free at netdev removal" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    can: peak_pci: prevent use after free at netdev removal

to the linux-3.13.y-queue branch of the 3.13.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11.4.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 3aed987cbac32cee1c98c95ae80058dfcede54d9 Mon Sep 17 00:00:00 2001
From: Stephane Grosjean <s.grosjean at peak-system.com>
Date: Tue, 20 May 2014 11:38:56 +0200
Subject: can: peak_pci: prevent use after free at netdev removal

commit 0b5a958cf4df3a5cd578b861471e62138f55c85e upstream.

As remarked by Christopher R. Baker in his post at

http://marc.info/?l=linux-can&m=139707295706465&w=2

there's a possibility for an use after free condition at device removal.

This simplified patch introduces an additional variable to prevent the issue.
Thanks for catching this.

Reported-by: Christopher R. Baker <cbaker at rec.ri.cmu.edu>
Signed-off-by: Stephane Grosjean <s.grosjean at peak-system.com>
Signed-off-by: Marc Kleine-Budde <mkl at pengutronix.de>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/net/can/sja1000/peak_pci.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/drivers/net/can/sja1000/peak_pci.c b/drivers/net/can/sja1000/peak_pci.c
index 065ca49..546a848 100644
--- a/drivers/net/can/sja1000/peak_pci.c
+++ b/drivers/net/can/sja1000/peak_pci.c
@@ -551,7 +551,7 @@ static int peak_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 {
 	struct sja1000_priv *priv;
 	struct peak_pci_chan *chan;
-	struct net_device *dev;
+	struct net_device *dev, *prev_dev;
 	void __iomem *cfg_base, *reg_base;
 	u16 sub_sys_id, icr;
 	int i, err, channels;
@@ -687,11 +687,13 @@ failure_remove_channels:
 	writew(0x0, cfg_base + PITA_ICR + 2);

 	chan = NULL;
-	for (dev = pci_get_drvdata(pdev); dev; dev = chan->prev_dev) {
-		unregister_sja1000dev(dev);
-		free_sja1000dev(dev);
+	for (dev = pci_get_drvdata(pdev); dev; dev = prev_dev) {
 		priv = netdev_priv(dev);
 		chan = priv->priv;
+		prev_dev = chan->prev_dev;
+
+		unregister_sja1000dev(dev);
+		free_sja1000dev(dev);
 	}

 	/* free any PCIeC resources too */
@@ -725,10 +727,12 @@ static void peak_pci_remove(struct pci_dev *pdev)

 	/* Loop over all registered devices */
 	while (1) {
+		struct net_device *prev_dev = chan->prev_dev;
+
 		dev_info(&pdev->dev, "removing device %s\n", dev->name);
 		unregister_sja1000dev(dev);
 		free_sja1000dev(dev);
-		dev = chan->prev_dev;
+		dev = prev_dev;

 		if (!dev) {
 			/* do that only for first channel */
--
1.9.1